The present invention relates to drop-outs for attaching bicycle axles to bicycle frames and front forks.
The front and rear axles of a typical bicycle are attached to the front fork and frame, respectively, of the bicycle. In particular, the axles are retained in slotted elements called "drop-outs" which are welded to receiving tubes of the front fork and frame, respectively. Depicted in FIG. 22 is a rear axle drop-out 1 which includes a slot 2 for receiving a bicycle rear axle. The drop-out 1 also includes a pair of legs 3, 4 secured in receiving tubes 5, 6 of a bicycle frame. In FIG. 23 there is depicted a front axle drop-out 7 which includes a slot 8 for receiving a bicycle front axle, and a leg 9 securable in a receiving tube 10 of a front fork of the bicycle.
Various techniques have been proposed for incorporating dropouts in bicycle frames. For example, in a "slotted tube" technique, as depicted in FIG. 24, a flat front axle dropout 7 has been inserted into the center of the end of the receiving tube 10. That end of the receiving tube is then worked to form dome-like transitions 16 between the cylindrical shape of the receiving tube and the flat sides of the dropout 7.
A variation of the slotted tube technique commonly called the cover plate method, involves locating the drop-out leg to one side of the tube rather than being centered therein. A cover plate is positioned over the opening between the opposite side of the tube and the drop-out leg. The cover plate and drop-out leg are welded to the tube and to each other.
Yet another drop-out securing technique, called the plug method is depicted in FIG. 25. That technique involves inserting a plug 18 into the receiving tube 5 and then welding it to the tube such that the plug projects beyond the end of the tube. A slotted element 1 is then welded to the exposed end of the plug.
Another technique, depicted in FIGS. 20, 21 and 26, and described in commonly assigned U.S. Pat. No. 5,025,977 involves bending a rear end 20 of a flat strip and machining that bent rear end to form a generally cylindrical portion 22. That portion 22 is inserted to a beveled end 24 of the receiving tube 5 and is attached thereto by a weld 26, or alternatively by brazing or gluing. The dropout can be provided with shoulders 26 to limit the insertion of the cylindrical portion 22 into the tube 5. In FIG. 26 there are depicted two dropouts 20 mounted in the thin-walled receiving tubes 29 of a front fork 28 of a bicycle frame.
An axle (not shown) will be clamped between two opposing inner surfaces 30 of the dropouts 20. Therefore, it is desirable that the area of each surface 30 be of a certain minimum amount to enable a proper clamping to occur. Also, since the slotted part of the dropout is usually of a thin, plate-like shape, whereas the ends of the fork tubes are of cylindrical shape, it is necessary to provide a transition between each tube and its dropout for atheistic reasons and also to avoid the presence of sharp corners which could risk injury to a rider or his clothes. It will be appreciated that the above criteria can be fulfilled by the earlier described dropout-forming techniques. However, each of those techniques involves either an appreciable amount of custom shaping of the tubes or an appreciable amount of fit-up and welding time. For example, the FIG. 24 technique requires that the tubes be specially shaped to form the dome-like transitions 16. The FIG. 23 technique eliminates a custom shaping of the tubes, but requires that two welding operations be performed to form a dropout.
The FIG. 20-21 technique requires a custom shaping of the tube, an that bending and machining operations be performed in order to make the dropout.
Similar considerations exist with respect to rear dropouts. Moreover, in the case of a one-piece rear axle dropout, it is necessary to provide that dropout with two mounting portions which attach to the seat stay tube and chain stay tube, respectively, of the frame. It is thus necessary that the angular relationship between the two mounting portions of the dropout correspond to the angular relationship between the seat stay tube and chain stay tube to which those mounting portions are to be attached. That means that for different bicycle sizes (having different angularly related seat and chain stay tubes), dropouts of corresponding sizes must be provided. That requirement significantly increases the overall manufacturing costs and difficulty.
It would be desirable to provide novel front and rear axle dropouts and methods of making same which alleviates the above shortcomings.
Another aspect of dropout-installation relates to the manner of adhering the dropout in its receiving tube. In some cases the dropout is adhered by an adhesive, whereas in other cases the dropout is adhered by a weld. When welding is performed, it is necessary to manipulate a filler wire, which contributes to the overall complexity of the manufacturing process. Also, the application of too much heat during the welding process can damage the thin-walled receiving tubes.
Therefore, it would be desirable to enable dropouts to be more easily welded to thin-walled tubes, especially titanium tubes, without damaging the tubes.